Corrosion may be defined as a natural process that occurs between a material and its surrounding environment. The process converts the material to a more chemically-stable form, such as an oxide, hydroxide, or sulfide of the material. However, corrosion may degrade the useful properties of a material or structure, including effects on strength, appearance and permeability to liquids and gases.
Thus, corrosion of metals is a significant and destructive process, resulting in economic losses across a wide range of industries. As an example, metals used in industrial structures may be oxidized and corroded due to exposure to harsh environmental conditions such as marine environment and moisture, which may subsequently lead to a deterioration of the mechanical properties of the structures. Therefore, corrosion may result in financial damages, with major impact on the economics of industries. It can be understood that the field of corrosion protection may play an important role in a wide range of industries such as oil and gas, petrochemical, and marine industries in order to help provide long-lasting structures.
Generally, conventional corrosion prevention methods have been based on eliminating or suppressing the chemical reactions which result in corrosion of materials. For purposes of reference, corrosion prevention methods may be divided in three different categories, though they may be combined: (a) cathodic protection; (b) corrosion resistant coatings, and (c) inhibitors. The most commonly used method for preventing corrosion of metals is application of a corrosion resistant coating on a metal substrate to prevent contact between the corrosive medium and the metal substrate. While conventional coating compounds often offer corrosion protection properties, they are associated with issues such as short service life, toxicity, high production cost, and instability.
Another group of anti-corrosion coatings that have been widely employed for corrosion protection of metallic structures in various industries is organic coating. For example, organic coatings may generally refer to epoxies, polyurethanes, silicones, alkyds, and other resins and polymers, which protect the metal by imposing a physical barrier between the metal surface and the corrosive environment. The barrier protection of organic coatings may occur by impeding the transport of aggressive agents through low permeable coatings to the surface of the substrate.
However, the applications of organic coatings may be restricted due to their inherent properties. For example, these organic coatings can have low resistance against penetration of corrosive agents such as water, oxygen, and ions, leading to disbondment of the coating at the metal/coating interface, which further leads to corrosion of the metal. Therefore, to overcome the aforementioned issues, carbon-based materials with a high specific surface area, such as carbon nanotubes, carbon black, and graphene may be used as nano-fillers in order to enhance the mechanical properties and corrosion resistance of organic coatings.